The invention relates generally to semiconductor devices, e.g., integrated circuits, and relates more particularly to the cooling of integrated circuit chips. Specifically, the present invention relates to a thermal interface for chip cooling.
Efficient cooling of integrated circuit (IC) devices is essential to prevent failure due to excessive heating. Efficient cooling of the IC chips depends in large part on good contact between the chips and the heat sinks or thermal spreaders, because a major part of the heat resistance budget is expended between the chip and the heat sink.
Conventionally, heat transfer between a chip and a heat sink is facilitated by providing a thin layer of thermally conductive paste or grease disposed between opposing surfaces of the chip and the heat sink unit. Typically, the layer of paste is approximately 100 microns thick and is mechanically compliant to conform to the sometimes irregular surfaces of the chip and heat sink.
Such conductive pastes have generally proven to be reliable in facilitating heat transfer; however, the thermal conductivity of conventional pastes is typically limited (e.g., typical pastes have a thermal resistance of approximately 10 to 100 mm2-° C./W). Thus, these pastes are only practical for use with relatively low-power IC chips. Moreover, heavy thermal cycling may cause non-uniform behavior in conventional pastes, or may cause conventional pastes to fail to thermally bond the chip to the heat sink, resulting in thermal run-away and also limiting chip cooling.
Thus, there is a need for a thermal interface that is capable of establishing reliable thermal contact, and of providing sufficient thermal conductivity and mechanical compliance between a semiconductor device and a heat sink.